Perl: Theory vs Practice

By Xah Lee. Date:

Randal L Schwartz quoted:

The difference between theory and practice in theory is much less than the difference between theory and practice in practice.

Popular quotes have attributes of equivocal interpretation and theatrical display. When interpreted and pondered by the wise, it lights up a wisdom, but dullards quote them equally, and delight in their drama. (the latter happens a lot in Perl and unix communities.)

From American Heritage Dictionary:

theory n. pl. theories: 1. a. Systematically organized knowledge applicable in a relatively wide variety of circumstances, especially a system of assumptions, accepted principles, and rules of procedure devised to analyze, predict, or otherwise explain the nature or behavior of a specified set of phenomena. b. Such knowledge or such a system. 2. Abstract reasoning; speculation. 3. A belief that guides action or assists comprehension or judgment: rose early, on the theory that morning efforts are best; the modern architectural theory that less is more. 4. An assumption based on limited information or knowledge; a conjecture.

The word 'theory', in practice, has more meanings than in theory.

For example, in the above sentence, ‘theory’ is used twice. In the first instance, it is used for a purpose but not for its meaning. It is part of a construction in a language that discuss the language itself. In theory it does not come up, but in practice it does all the time. In practice, we can say that the first instance of usage of the word ‘theory’ has no meaning given the context. In the second appearance of the word, it has myriad of interpretations due to the construction of the phrase.

People may mean: “The word ‘theory’, in practice, has more meanings than people would think.” Here the word is thus used conveniently to stand for “mob's knowledge”.

From a logical linguist's mouth, the intent might be: “The word ‘theory’, outside academia, acquire more meanings and purposes than we require in linguistics.” The sensibility of such semantic content is demonstrated in the previous paragraph.

People may say: “in theory, tomorrow'll rain.” They really mean “the broadcast station lady said that tomorrow will rain.”

A detective might say, “in theory, that guy is the murderer.”. He really means: “according to my investigations, it is highly probably that that guy is the murderer.”. (dictionary definition #4.)

In a strict sense, ‘theory’ means systematic and organized principles derived by scientific means (dictionary definition #1.). In a more strict mathematical sense, ‘theory’ is the body of theorems, and theorem by definition describes practices correctly always, else it is not a theorem. It is possible for a mathematical theorem to be incorrect (we are humans, after all), but in practice to assume that theorems can be incorrect is like assuming one might be hit by a meteor tomorrow. Theoretically correct, but not sensible.

As you can see, the word ‘theory’ is subject to wanton abuses. In fact, all English words are subject to extraneous purposes to yield sentences or paragraphs that has a meaningful ambiguous interpretation. (this is how poetry works, in theory.) All in all, English is extremely malleable and ambiguous. The phrase “The word ‘theory’, in practice, has more meanings than in theory” is really silly, except in really well-defined context. In our context, the quote amounts to illustrating the stupidity of Perlers who don't have a solid background in logic or linguistics, but like to quote about differences of theory vs. practice.

Larry Wall likes to mention how he had a linguistics background, and how he utilized the (good) human qualities of English to create Perl. To the Perl folks of beady eyes, they are sold a grand advance in computer science, but to discerning eyes, it's artful garbage.

Sorry i don't have time to address the above points of Wall's, but this will definitely be another lesson for you folks down the road.

The Perl folks with their beads of little eyes, cannot see beyond imperative languages.


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  1. Laziness, Perl, and Larry Wall
  2. Perl's raison d'être
  3. Perl: Theory vs Practice
  4. The Unix Pestilence: Theory vs Practice, II
  5. Larry Wall and Cults
  6. On the Survival Strategies of Larry Wall vs Richard Stallman